Voting-rights advocates in Pennsylvania filed suit on Thursday to nullify the state’s congressional-district map as an unconstitutional partisan gerrymander, joining other court battles over the role of politics in redistricting already being waged in three other states.

It is the latest major legal effort arguing that gerrymanders have become so egregious they are subverting democracy and creating legislative races with predetermined results.

In a tactical twist, however, the Pennsylvania lawsuit was filed in a state court, which means that if the plaintiffs prevail, the ruling would set no precedent for challenges in other states.

The three other lawsuits, in Maryland, North Carolina and Wisconsin, were filed in federal court and argue that the maps of congressional or state legislative districts violate the federal Constitution.

Pennsylvania Republicans called the lawsuit baseless. In a statement, Drew Crompton, the general counsel for Republicans in the State Senate, said that the redistricting measure was enacted with some Democratic support and that some claims in the suit were “demonstrably false.”

“Serious concerns exist concerning the disenfranchisement of 12 million Pennsylvania voters if any court sides with the plaintiffs and changes the rules six years after the plan was properly passed,” the statement said.

The suit contends that the Republican-controlled state legislature redrew congressional district boundaries in 2011 with the aim of creating as many unassailable Republican House seats as possible. Pennsylvania has five registered Democrats for every four registered Republicans, but Republicans control 13 of the 18 congressional districts.

The lawsuit noted that Republicans captured those 13 seats in 2012, in the first election after the boundaries were redrawn, even though they won only 49 percent of the vote statewide.

Democrats and Republicans draw political maps to entrench themselves in power, said Chris Carson, president of the League of Women Voters, whose Pennsylvania chapter is a plaintiff in the suit. But Republicans have gained a lopsided majority of House seats since 2011, partly because of a national campaign nicknamed Redmap aimed at controlling the redistricting process. “Both sides do it when they have the opportunity, and it has a long and glorious history,’’ Ms. Carson said. “But it’s got to stop.”

While it has long been illegal to draw political boundaries to dilute the voting power of minorities, federal courts have been flummoxed by whether gerrymanders designed to weaken political opponents can be identified, and, if so, how.

The three federal lawsuits attack the issue from two sides. Two of the suits propose a simple mathematical formula to measure the partisan effect of new maps. All three contend that partisan gerrymanders violate the First Amendment, not only because they dilute the voice of political factions but because they amount to retaliation against them for expressing their political views.

The Wisconsin lawsuit, which introduced the new formula to gauge the partisan effect of maps, is now before the Supreme Court, which could decide as soon as next week whether to hear the case. Two North Carolina lawsuits have been consolidated and will be heard by a three-judge panel of the United States District Court in Greensboro on June 26.

Both of those lawsuits challenge political maps drawn by Republican legislatures. The Maryland suit challenges a Democratic-drawn map of House seats.

The Pennsylvania lawsuit relies on the freedom-of-speech argument to attack the state map of House districts. But it spurns the federal Constitution’s First Amendment guarantees in favor of those in the state Constitution, which plaintiffs say more broadly protects free speech.

Indeed, the lawsuit argues, state courts have made that explicit, particularly in a landmark decision in 2002 that stopped officials in Erie from outlawing nude dancing in an establishment called Kandyland. In that decision, the court noted the state Constitution expressly forbids muffling a citizen’s voice.

David P. Gersch, a lawyer for the plaintiffs, said the current map punishes Democratic voters because of their political views. “Surely the state’s voters are entitled to at least as much protection as naked dancers,’’ he said.

A version of this article appears in print on , on Page A14 of the New York edition with the headline: Pennsylvania Lawsuit Is Latest to Call House Redistricting a Partisan Gerrymander. Order Reprints | Today’s Paper | Subscribe